Tornado Alley
The prairie or the Great Plains, which is found in the US Midwest, is the place on Earth with the greatest risk of tornado formation. During the months of spring, cold and dry polar air comes from the north and from the south warmer and moister tropical sea air from the Gulf of Mexico. The encounter between the two air masses and the fact that the sunlight begins to heat the great, flat prairie are the main factors causing the particularly forceful shower and thunder systems that produce the tornadoes. The Midwest is the place on Earth in which the most tornadoes form, and so, the region is also known as Tornado Alley.
There are averagely some 800 tornados in the entire United States throughout the tornado season from March to August. The busiest time of the season is in April, May, and June, when 55+ % of the tornadoes are produced, but they can occur throughout the year.